Re: st: differentiating between groups of records with same date

bysort patient_no diag_date: gen freq = _N
See also
SJ-2-1 pr0004 . . . . . . . . . . Speaking Stata: How to move step by: step
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox
Q1/02 SJ 2(1):86--102 (no commands)
explains the use of the by varlist : construct to tackle
a variety of problems with group structure, ranging from
simple calculations for each of several groups to more
advanced manipulations that use the built-in _n and _N
Nick
On Mon, Jul 30, 2012 at 10:20 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:
> Hi all,
>
> I have a group of patients who are in a dataset of cancers. Each patient may have more than one cancer diagnosed, and so may be present in my dataset a number of times. Each patient has a unique patient identifier, and each cancer has a unique cancer identifier. Each row of data is cancer specific, but does contain the patient identifier. It is possible that a patient has 2 cancers diagnosed on the same day in my dataset. What I would like to do is generate a flag next to each record to show against each cancer the number of cancers diagnosed on the same day.
>
> My data are like this:
>
> patient_no cancer_no diag_date surgery_date
> 9512834 0484360 21may1994 21may1994
> 9512834 0484358 21may1994 21may1994
> 9512834 0483234 26apr2000 21may2000
> 9512834 0483233 26apr2000
> 0000057 0000057 19jul2009 19jul2009
> 0000060 0000060 02nov2009 24nov2009
> 0000074 0000074 21sep2009 22nov2009
>
>
> For example, patient 9512834 had 2 cancers diagnosed on 21may1994 and so for cancer_no 0484360 and 0484358, I would like to generate a new variable with the value 2 against each record. Similiarly patient 0000057 has only one cancer diagnosed, and so the new variable would contain 1.
>
>
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